DMI:DSResponse.getDataList returns null, while query works

Smart GWT Technical Q&A
1

[Using the Power nightly of 06-30-2011]

Hello,

I have a DMI that does an extra DSRequest that does some extra fetch. The problem is that while the query works and returns 6 rows, myDSResponse.getDataList() returns null.

The DMI looks like this:

public DSResponse remove(DSRequest req) throws Exception {
	//fetch all lecture_presence_rows of this 
	DSRequest presence = new DSRequest("Lecture_presence_Student", "fetch");
	presence.setOperationId("AlsoJoinOnCourseEdition");
	presence.setRPCManager(req.getRPCManager());
	presence.setCriteria("students_id", req.getFieldValue("students_id"));
	DSResponse resp = presence.execute();
	List data = resp.getDataList();
	// ****** data is null here, while query worked! and actually returned 6 rows.
}

The query worked:

=== 2011-07-05 10:25:50,435 [l0-5] INFO  SQLDriver - [builtinApplication.AlsoJoinOnCourseEdition] Executing SQL query on 'Mysql': SELECT Student.phone, Lecture_presence_Student.reason, Student.sofinummer, Student.street, Student.surname, Student.city, Student.voorletter, Student.archived, Student.cellphone, Student.birthdate, Student.gender, Lecture_presence_Student.presence_id, Student.number_addition, CourseEdition_students_Student.students_id, Lecture_presence_Student.status, Student.tussenvoegsel, Student.number, Student.firstname, Student.postcode, Student.country, Student.birthplace, Student.email, Student.Moodle_id, Student.active, CourseEdition.CourseEdition_id FROM Lecture_presence_Student 
                   INNER JOIN Student ON Lecture_presence_Student.Student_id = Student.Student_id 
                   INNER JOIN Lecture ON Lecture_presence_Student.Lecture_id = Lecture.Lecture_id
                   INNER JOIN CourseEdition_students_Student ON CourseEdition_students_Student.Student_id=Student.Student_id
                   INNER JOIN CourseEdition ON Lecture.CourseEdition_id=CourseEdition.CourseEdition_id 
       WHERE (CourseEdition_students_Student.students_id='95')
=== 2011-07-05 10:25:50,471 [l0-5] INFO  DSResponse - [builtinApplication.AlsoJoinOnCourseEdition] DSResponse: List with 6 items

This is the ds.xml operationBinding In question:

    <operationBinding requiresRole="ROLE_USER" requiresAuthentication="true" operationType="fetch" operationId="AlsoJoinOnCourseEdition" > 
      <tableClause>Lecture_presence_Student 
                   INNER JOIN Student ON Lecture_presence_Student.Student_id = Student.Student_id 
                   INNER JOIN Lecture ON Lecture_presence_Student.Lecture_id = Lecture.Lecture_id
                   INNER JOIN CourseEdition_students_Student ON CourseEdition_students_Student.Student_id=Student.Student_id
                   INNER JOIN CourseEdition ON Lecture.CourseEdition_id=CourseEdition.CourseEdition_id 
      </tableClause> 
    </operationBinding>

Am I doing something wrong, or is this a bug? When step-debugging, the object actually DOES contain a JSON string of the returned rows… Bug in API?

2

At a glance this is just not possible: setData() is printing out the log about the number of items so a subsequent call to getData() cannot help but retrieve the data setData() has just stored under the key “data”.

setParameter is equivalent to setProperty()/getProperty(). Can you use these APIs to tell us what’s under the “data” property when this getDataList() API isn’t working for you?

public void setData(Object data) {
    setParameter("data", data);
    if (data instanceof List) {
        long rowCount = ((List)data).size();
        log.info("DSResponse: List with " + rowCount + " items");
    } else if (data instanceof Map) {
	long rowCount = ((Map)data).size();
        log.info("DSResponse: Map with " + rowCount + " keys");
    }
}

public List getDataList() {
    Object data = getData();
    if (data instanceof JSONFilter) data = ((JSONFilter)data).getObj();
    if (data instanceof List) return (List)data;
    return null;
}

public Object getData() {
    return getParameter("data");
}
3

Okay, thanks.

This returns an JSONFilter object:

Object o = response.getData();

It is indeed pretty strange cos there’s not htat much happening, and on other parts where I use similar code, it works.

I did this as a workaround, and now it works

DSResponse resp = presence.execute();
//List data = resp.getDataList();
Object d=resp.getData();
JSONFilter j = (JSONFilter) d;
List data = (List) j.getObj();

I have no idea why this would happen…